How do I make the money?

So I was just thinking about implementing ads into my game, but I just need to know, how do I get money, am I supposed to register somewhere or what?

Point 1 in the manual: https://www.scirra.com/manual/184/admob

—, how do I phrase it so that a banner ad shows on start of a layout

— just search for AdMob tutorials. It's really self explanatory so you can also simply check AdMob object functions.

AdMob -> Show banner